Edged tools, in particular for wood working such as plane irons, wood chisels or spoke shave blades generally need to have a sharp edge with a well defined shape. In certain applications, the tool, e.g. a plane iron, may have a so called straight edge in which the front of the edge generally forms a 90° angle with the sides of the tool. In other applications, the edge of the plane iron may have a generally cambered shape.
Sharpening of the tools is typically performed in a grinding machine which comprises a rotating grindstone and a grinding jig to assist the operator to maintain the angle of the edge of the tool during grinding.
When grinding straight edged tools it is important to maintain the faces of the tool in parallel orientation with the grinding surface of the grindstone. This is so because the front of the edge of the tool will be ground skew if the face of the tool is oriented in an angle with respect to the surface of the grindstone.
This problem has been addressed in EP 1987916 B1 which shows a grinding jig comprising a base provided with a vertical shoulder and a plane support surface for supporting the face of the edged tool. A clamp is movable against the support surface by means of two screws which extends into the clamp through holes in the base on either sides of the support surface. When the tool is clamped in the jig by tightening of the screws, the support surface and the shoulder guides the face of the tool into parallel orientation with the grinding surface of the grindstone.
However, although the grinding jig disclosed in EP1987916 B1 has proven to be very effective, an inexperienced operator may face difficulties in tightening the screws of the clamp in a proper manner, e.g. one screw may be tightened harder than the other. This may result in an uneven clamping pressure across the tool which forces the face of the tool into misalignment with the grinding surface and results in a skewness of the tools edge after grinding.
Thus, it is an object of the present disclosure to provide a grinding jig which addresses at least one of the aforementioned problems.
In particular, it is an object of the present disclosure to provide a grinding jig which allows for simplified alignment between the front edge of the tool and grinding surface of the grindstone. A further object of the present disclosure is to provide a grinding jig which allows for high accuracy of the alignment between the tool and the grinding surface of the grindstone. A further object of the present disclosure is to provide a simple but yet robust grinding jig which may be produced at low cost.